Telephone-exchange system



H. P. CLAUSEN.

TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED JUNE 25. 1917.

1,345,349. Patented ly 6, 1920.

//7 ran /or.' Henry R [/aasen accompanying drawings, wherein UNITED STATES PATENT OFFICE,

HENRY 1?. CLAUSEN, OF MOUNT VERNON, NEW YORK, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORA- TION OF NEW YORK. I

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented July 6,1920.

Application filed June 25, 1917. Serial No. 176,809,

This invention relates to telephone exchange systems, and more particularly to such systems in which telephone lines terminating at different switchboards maybe connected together by means of trunk circuits. t

In systems of this type, commonly known as the A-B- toll systems, in which a toll telephone line may be'connected directly with or through a connecting circuit to an Aboard, and is then connected, by means of a link circuit at the A board and a trunk circuit extending from the A to the B board, with another telephone line, usually a local line terminating at the B board. In systemsof this character it .is usual to give the operator at the Aboard complete supervision of the connection, and it is also common practice to employ a trunk circuit of the so-called machine ringing or automatic type. With systems of this character, it is frequently desirable to build up the connection from the link circuit at the A board, through the trunk circuit, to the local telephone line and to hold this line while the connection between the link circuit and the more expensive toll telephone line is being built, and to enablethe operator upon this latter connection being completed.

to cause the connection of ringing current with the local line, which may thereafter be automatically disconnected therefrom in the usual manner; It is also desirable at times to signal the local wanted line immediately upon the connection being set up from'an A board through the link and trunk circuits to the wanted line. a It is the object of this invention-to provide a system in which there is a trunk cir cuit which may be employed to accomplish the desirable results above set forth. For a more complete understanding of this invention, reference should be had to the description considered in connection with the Figure 1 shows a telephone exchange system containlng one embodiment of this invention; and Fig. 2 shows a modified form thereof.

In Fig. 1 there is a telephone line A, whlch may be connected in any desired manner with'the cord circuit C, located at a central flice X, and another telephone line B term nating at avcentral office Y, at which is located the incoming end of a trunk circuit D, the outgoing end of which is located at the central office X.' For convenience,

{the operator at the central office X will hereinafter be designated as the A operator,

and the operator at the central oflice Y, as I the B operator.

Assuming that it is desired to build up a connection with and hold line B while the connection with line A is being built and to delay the application of the ringing current i to line B until the connection with line A has been built up, the A. operator"com municates with the B operator over an order wire circuit (not shown) and receives a trunk assignment and then inserts plug 5 of the cord circuit G into jack 6 of the trunk circuit D, and the B operator inserts plug 15 of the trunk circuit D into jack 16 of line B. The insertion of the plug5 into the jack 6 causes the lighting of calling c.

supervisory lamp 8,-and the operation of v Supervisory relay 10 does .not operate when in series with the high retrunk relay 9.

sistance right-hand winding of relay 9 and the winding of polarized'relay 11, but does operate when thevlow resistance left-hand winding of relay 9 is connected in parallel with the right-hand winding thereof and the winding of polarized relay 11, as will hereinafter more fully appear. Polarized relay 11 is so poled that it does not operatewhen the plug 5 is inserted into the jack ,6, but does operate when the plug 5 is inserted into jack 7, which reverses the direction of the flow of current over the circuit .includin operator has not inserted the plug 15 into the ,jack 16, the operation of relay 9causes the lighting of lamp 12 over a circuit from the winding of polarizedrelay 11. ,If the I battery through the lamp, contact of relay 9, lower normal contact of relay 1 3 and res'istance 14 to ground; but, if the plug 15 has been inserted into the jack 16, the lamp 12 will not be lighted by the operation of relay 9. The insertion of the plug 15 of trunk cir cuit D into the jack 16 of line B by the B operator causes the operation of relay 13 and cut-ofi' relay 17. Relay13, in operating, causes the operation of local relay 18 over a circuit from battery through the winding of relay 18, normal contact of relay 19, contact of tripping relay 25, the alternate contact of tripping relay 25 and the lower alternate contact of relay 18.

If, under these circumstances, the subscriber should remove the receiver from the switchhook, a circuit will be completed for tripping relay 25, which operates, removing the short circuit of relay 19, which then opcrates and locks up, establishing a short circuit for relay 18. 'Relay 18 then releases, opening its alternate contact and closing its normal contacts which are in the talking circuit. Supervisory relay 26 is thereupon operated to close a contact in circuit with the low resistance left-hand Winding of relay 9, thereby including this winding in parallel with the right-hand Windingof relay 19 and the winding of the polarized relay 11 to thereby reduce the resistance incircuit with supervisory relay 10. Relay 10 thereupon operates, closing a shunt path including'resistance 27 for'the lamp 8, which is thereby efi'aced. r

I Assuming, however, that subscriber B does not remove the receiver from the switchhook, while relay 18 is energized as the result of the connection of the plug 15 with the jack '16, and the connection of the plug 5'with the jack 6, and that the connection with'the telephone line A has been built up,'the A operator is'suitably advised, and thereupon removes the plug 5 from the jack 6 and immediately inserts this plug into jack 7; Relay 9 is slow-releasing, and does not open its contact while the plug 5 is being transferred from a jack 6 to a jack 7. The insertion of the plug 5 into the jack 7 reverses the direction of flow of current through the winding of polarized relay 11, thereby causing the operation of this relay to open its normal and close its alternate contact, thereby disconnecting battery from line B and substituting therefor a sourceof ringing current 29 for causing the operation of a call bell 28' at'the station of line B. Subscriber B, in response to the operation of the-call bell, removes the receiver from the switchhook, causing the operation of trip ping rela 25, whereupon the relay 19 0perates an locksup, and relay 18 releases in the manner hereinbefore described. Supervisory relays 26 and 10 also operatein the supervisory lamp 8. v

At the conclusion of the conversation, subscribers "A and B restore their receivers to the switch-hooks. Subscriber B, in restoring the receiver to the switch-hook,

manner .hereinbefore described to efiacethe causes the defe'nergization of supervisory relay'26, whereupon supervisory relay 10 releasesits armature, permitting the lamp 8 to light to furnish a disconnect signal. Tl1'e A? operator then withdraws the plug 5 from the jack 7, thereby releasing polarized relay 11 and trunkrelay 9. The release of relay 9 removes the'shunt circuit from lamp 12, which thereupon lights to furnish a disconnect signal to the, B operator, who withdraws the plug 15 from thejack 16,

thereby restoring all apparatus of the trunk circuit and the telephone dition.

line to normal 0011- f Should it have been desired to apply ring- 7 ing current to telephone line B immediately uponthe connection of the trunk circuit D with the line and the connection of the cord circuit C with the trunk circuit, the plug 5 would have been inserted into jack 7 in stead of jack 6. Polarized relay 11 would then be operated so that, as soon as relay 18 operated'followingthe insertion of the plug 1'5 into the jack 16, the source of ringing current 29 would be immediately connected-with line B.

If desired'a reversing key 3.0 such as is shown in Fi 2 may bej cfonnected in the cord circuit 6 in the place of conductors .31 and 32, and the jack 7 omitted. This key 30 is preferably. of the locking type, so that when in normalposition and the plug 5 inserted in the jack 6, the directionof the flow of current through the winding'of the polarized relayill is such that the relay is not operated. Upon the actuation of the key 80, the direction of the flow of current through the winding of relay 11 is reversed, causing the operation of the relay.

WVhat is claimed is: 1. A telephone exchangesystem comprising atrunkcircuit extending from a first to a energizing circuit therefor including a contact of the trunk relay completed: upon the connection of the trunk circuit with the telephone line, an operator-controlled switch at the first switchboard, a control. relay 'responsive to the actuation of the switch, and

a source of ringing current'connected with the telephone line through contacts of the local'and the control relay. w

2. A telephone exchange system comprising a trunk circuit extending from a first to a second switchboard, a link circuit at the first switchboard, a trunk relay energized over the talking strands of the trunk circuit upon the connection of the link circuit therewith, a telephone line terminating at the second switchboard, a local relay, an energizing circuit therefor including a contact of the trunk relay completed upon the connection of the trunk circuit with the telephone line, an operator-controlled switch at the first switchboard, a control relay in circuit with the talking strands of the trunk circuit oper ated upon the actuation of the switch, and a source of ringing current connected with the telephone line through contacts of the local and control relays.

3. A telephone exchange system compris ing a trunk circuit extending from a first to a second switchboard, a link circuit at the first switchboard, a trunk relay energized over the talking strands of the trunk circuit upon connection of the link circuit therewith, a telephone line terminating at the second switchboard, a local relay, an energizing circuit therefor including a contact of the trunk relay completed upon the connection of the trunk circuit with the telephone line, a source of current at the first switchboard, an operator-controlled switch thereat adapted when actuated to reverse the direcing a trunk circuit extending from a first to a second switchboard, a link circuit at the first switchboard connected with the trunk circuit, a telephone line terminating at the second switchboard, a relay responsive to the connection of the trunk circuit with the telephone line, a source of, current at the first switchboard, an operator-controlled switch thereat for reversing the direction of the flow of current over the talking strands of the trunk circuit, a polarized relay in circuit with the talking strands of the trunk circuit responsive to the actuation of the switch, and a source of ringing current connected with the telephone line through contacts of the two relays.

In witness whereof I hereunto subscribe my name this 22nd day of June, A. D. 1917.

HENRY P. CLAUSEN. 

